Treatment of fish water



Patented July 2. 1946 v TREATMENT OF nsn WATER Robert 0.. Ernst,Louisville, Ky assignor, by mesne assignments, to General AmericanTransportation Corporation, Chicago, Ill, a corporation of NewYork NoDrawing. Application February 19, 1945,

Serial No. 578,801

2 Claims. 1

This invention relates to the treatment of fish water, and moreparticularly to the treatment of fish water prior to its concentrationby evaporation to facilitate the evaporating step and produce a moredesirable product for stock feed.

In processes now employed to recover for stock feed and other productsincluding fish oil, it is the usual practice to cook fish usually by,

steaming it, press the oil and water from the cooked fish. press and drythe solids, and centrifuge the pressed liquid or otherwise separate thefish oil from the fish water. The fish War ter" is subsequentlyevaporated to increase, its 7 The present invention is directed to the{sub-- stantial elimination of the scale problem in treating fish water,and the production of an improved product, and has as itsprincipal'object an improvement in the processing of fish water wherebyscale formation is substantially eliminated and substantially allconstituents of the original water are-retained in solubleform which isparticularly desirable in the case of products intended for stock feed.v

A further object of this invention is an improvement in the process oftreating fish water concentration, the product obtained thei'eby beingeither returned to the pressed solids and dried therewith or marketedseparately as a high vitamin product.

In the processing of the fish waterto increase its concentration,multiple effect'evaporators of the tube type are employed. With suchevaporatorr, considerable difficulty has been encountered because of theaccumulation of scale which greatly reduces the rate of heat transferand the consequent efficiency and capacity of the evapoe rator, and alsoresults in the loss of valuable organic, and inorganic constituents ofthe. fish water such as phosphates. to such an extent that the tubes ofan evaporator may become entirely blocked after only 4 'or 5 hours ofoperation. The evaporator must then be taken out of service for a periodof from 24 to 48 hours to permit removal of the scale which is adifficult and expensive task.

Until the present invention, the formation of this scale has beenregarded as a necessary evil. An example of the attitude taken towardthis problem is found in the following quotation from Chemical EngineersHandbook (1934) published by McGraw-Hill Book Co. Inc. at page 936 underthe heading of Evaporation-scale formation and scale removal:

"If scale-forming substances are present, there is no way of preventingscale formation. The rate of scale formation may be decreased by usinghigh velocities or by introducing seed crystals of the scale-formingmaterial in suspension. Scale- 1 wherein the concentrating thereof isfacilitated and the maximum efficiency and capacity of the employedevaporators are maintained at all times.

In attaining the aforesaid objectives," the pres- 'e'ntinventioncontemplates the addition of an acid compound to fish water-prior to itsevaporation or concentration sufiicient to maintain the pH value of thewater in the acid range during the concentration, the added acidcompound being of a character substantially-to form only solublecompounds with the constituents of the water which compounds remainsubstantially soluble throughout the evaporating step. The

necessity for maintaining the solubility of sub Scale accumulates Istantially all the constituents down to a predetermined concentrationeliminates the pcssibil ity of using such acids as sulphuric acidbecause they produce scale-forming salts such as calcium sulphate. Informing this scale, the insoluble compounds have been found to occludeand absorb valuable organic constituents in their precipitation andcollection 'upon the tubes of the evaporator, 'thereby not only causingscale but also reducing the value of the ultimate aciditythroughout theevaporating step because templates the insurance -of an acid product.

Normally, the fish water resulting from the treatment of fresh fish isneutral or slightly alkaline.' In the case of rotten fish, the fishwater may be slightly acid but it does not retain this the organic acidstherein break down under the application of heat. The present inventionconcondition throughout the evaporation.

The acid compounds, which I employ to lower and maintain the pH value ofthe fish water in the acid range, embrace phosphorous acid, phosphorousacid compound and acid salts of phosphorous acid. These materials aresometimes called, and are herein designated, acidic phosphitic compoundsto distinguish them from the acidic phosphatic compounds such asphosphoric 9,408,174 r I I 4 acid. Among the acidic phosphiticcompounds. I with the addition of an acid compound as de- =arephosphorous acid (HsPOa), hypophosphcrous scribed, it has been foundthat the problem of acid (HsPOz), phosphorous trlchloride (PCLa), scaleaccumulation has been substantially solved phosphorous oxide or'anhydride (PzQa); phosand that substantially all the originalconstitujphorous salts such-as phosphorous tri-bromide 5 cuts of thefish watervare retained. when an (PBrg), phosphorous iodide (P11) andphosphoacid compound such as phosphorous acid is emrous sulphide (Pass),these latter salts not being ployed, the resulting product has beenfound to highly recommended because they are both diibe greatlyincreased in soluble phosphate con 3 ficult to handle and expensive. Inthe prepatent, thereby increasing its value as a stock ieed. ,ration ofa product that is to be used for stock The use of phoshorous acid hasbeen found to 1 feed, a definitely nontoxic compound such as haveanother advantage in that it functions to phosphorous acid is preferablyemployed because inhibit corrosion of the evaporator tubes, particof itscontribution to the soluble phosphate conularly in the case of irontubes, and materially 1 tent of the final product. In the case of hos-.increases their life.

phorous acid, acid of a commercial grade or 15 This application, aspreviously noted, is diabout concentration is preferably added in rectedto acidic phosphiticcompounds which emthe proportion of 4.5 to 6.0pounds to 1000 galbraces phosphorous acids, phosphorous acid comlons oifish water, this proportion normally bepounds and the acid salts of pphorous acid. in; uffici nt to aint i the pH lu of th My co-pendingapplication, Serial No. 423,034, fish water in the acid range throughoutthe evapd e er 1 ,1s directed to acidic p 1 crating step. In the case ofthe phosphorous Ph Compounds which embrace phosphoric 3 acid compoundsand the acid salts of phosph'oacid; Pho p r i mp unds and the acid rousacid, enough of such material is added to salts of phosphoric-acid. I

1 insure a pH value remaining in the acid range Having described my in Iclaim: I throughout the evaporating step. The foregoing 25 1 Animprovement in the process of treating J proportions of acid or acidicmaterial is subfish water by evaporation to increase the constantiallyin excess of the amount of acid which centration thereof andsimultaneously maintain ha heretofore been added t fish water to fix thesolubility of the constituents thereof com-. the ammoniacal constituentsof the fish water. prising: adding, to the fish water, a quantity of 1Th s acid ha heret t r be n added to onv rt an 'acidic phosphiticcompound sufllclent to the ammonia into relatively stable salts but themaintain the pH of.the water in the acid range amount of the additionhas been such to render during evaporation, said acid compound being thefish water neutral after the conversion. of a character to form onlycompounds which re- Preferably, the acid compound is metered into mainsubstantially soluble throughout the evapthe fish water immediatelyprior to its entry into orating step. a

the evaporator whereupon evaporation can be 2. The process of claim 1wherein said acid conducted to the limit of solubility oi the-leastcompound is phosphorous acid. soluble compounds. ROBERT C. ERNST.

